This paper describes a new system capable of detecting small capacitance variations coming from an integrated micromachined sensor element. As an example of the possibilities the realization of a pressure sensor will be shown. The signal, containing the information of the physical situation, is detected by an especially designed bridge input stage, built into the first integrator of a Sigma Delta Modulator (SDM). The output signal is an oversampled one-bit representation of the desired information. It is already converted to digital and has been noise shaped by the modulator structure. Due to its noise insensitivity this signal would be well suited for a digital transmission to a receiving station where it could undergo the needed postprocessing. In this realization one step is gone further and a digital signal reconstruction on chip has been provided. By doing this a parallel digital word ready for a myP-System has been obtained. To avoid the need of a large amount of pins a serial data transfer protocol is implemented which requires only three pins. Building blocks and chip architecture are depicted in the paper. The system runs from a supply voltage of 5 V, and is internally clocked at 400 kHz. The decimated sampling frequency is nearly 1.6 kHz and the cutoff frequency is nearly 400 Hz.
A monolithic myP-ready sum of delta readout circuit with integrated capacitive sensors
Beschreibung eines monolithischen Mikroprozessorsystems zur Identifikation von geringen Betriebsänderungen kapzitiver Sensoren am Beispiel von Drucksensoren
1996
6 Seiten, 7 Bilder, 3 Quellen
Conference paper
English
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